DE69839231T2 - Copy protection method for a record carrier - Google Patents

Description

The The invention relates to a copy protection method for a record carrier, a copy-protected record carrier and a method of detecting access control information.

A copy protection system for a record carrier, a copy-protected record carrier, and a read device are off EP-0545472 known (document D1 in the list of related documents). The known recording medium comprises a previously arranged guide track, a so-called preliminary groove. In the track determined by the pregroove, information written in a previously defined manner is represented by optically readable patterns formed by a change of a first physical parameter, such as a. B. the height of the scanned surface. The pregroove has changes in a second physical parameter, such as. B. a deflection in a transverse direction, which is also referred to as wobbling. Vorfillenwobbelung is FM-modulated and this modulation represents access control information associated with information such. A descrambling code for retrieving information stored as scrambled information. The known device comprises reading means for reading out the patterns and recovery means for retrieving the access control information. The known device and the information carrier form a system for controlled information reproduction. For this purpose, the device comprises means for displaying the information in dependence on the access control information. When the information is copied to a recordable information carrier, the information of that copy is not reproduced because only the patterns are written during the writing process and the copy itself does not contain access control information. A problem with the known system is that the reading means must be able to recover the access control information by recognizing the changes in the second physical parameter.

It should be noted that WO 95/03655 (Document D3) describes a CD-PROM encryption system in which the information on a CD-ROM is encrypted by a key, which key is programmed into the CD-ROM after manufacture, destroying selected sectors so that they are of conventional design Reading systems can not be read. The selected sectors are physically destroyed by a high power laser. Record carriers are activated individually by having a specific key for a particular user or group of users.

Of the The invention has for its object to provide a copy protection system for record carriers, not on changes based on physical parameters, the production of useful copies on recordable information carriers counteracted becomes. The invention is defined by the independent claims. The dependent claims define advantageous embodiments.

Further advantageous preferred embodiments the copy-protected Recording medium, the recovery arrangement and inventive method will be described below.

EP-A-0 533 204 discloses an information recording / reproducing apparatus having a protection function for protecting information recorded on an information recording medium. The information on the information recording medium is protected from access by performing a data conversion process after the normal error encoding, so that the error correction capabilities are exceeded. In the embodiments, the process of converting the data is based on a secret that the reader must be aware of in order to access the data. Knowledge of this secret transmitted separately from the information recording medium allows the reader to perform inverse data conversion while reading the data. Then the normal error correction takes place. Without knowing this secret, the reader can not read the data because many uncorrectable errors are detected, thereby exceeding the reader's error correction capabilities.

embodiments The invention are illustrated in the drawing and will be described in more detail below. Show it:

1 a copy-protected record carrier

2 a logical mapping of the recording area of a copy-protected recording medium

3 an error correction unit

4 a bit error pattern

5 an arrangement for retrieving information from a copy-protected record carrier

6 a schematic representation of a copy protection for a recording medium.

1 schematically shows a plate-shaped copy-protected recording medium 1 , The record carrier comprises a track 9 for storing information which track in a spiral pattern of turns around a central hole 10 is arranged. The windings may also be arranged concentrically instead of spirally. The record carrier 1 is of the optically readable type, in which a transparent substrate is covered by a recording layer and a protective layer, such. B. the well-known compact disc (CD). Information on the information carrier is represented by patterns of optically readable marks. For example, the position and / or the length of the marks then represent a binary information signal. The marks can be made by pressing, as is common for read only CDs, such. For example, the CD-ROM on which embossed pits and ridges between the pits represent the information. The invention may be used for any type of media on which information is recorded in accordance with previously determined error correction rules, such as: For example, the high-density DVD (Digital Versatile Disc) optical disk, optical tape or magnetic tape for digital video. The track 9 includes the marks and can be scanned by a reading head for reading the stored information. The marks represent a bit sequence according to a channel code, such as a channel code. EFM for CD (eight-in-fourteen modulation). The bit sequence represents information according to previously determined error correction and formatting rules, such as: B. CIRC (Cross Interleaved Reed-Solomon Code) for CD. In accordance with the formatting rules, the record carrier may be divided into addressable sectors, such as: On the CD-ROM. The CD-ROM is described in ISO standard 10149, the CD-ROM specification.

The information on the copy-protected record carrier 1 include main information and access control information for controlling access to the main information so as to prevent access to main information copied to an illegal copy, the copy not including any necessary access control information. According to the invention, the copy-protected recording medium 1 with logic errors 2 which logic errors constitute an error pattern representing at least some of the access control information. The error pattern has at least one logic error at a predetermined location, but preferably a pattern of logic errors at a relatively large number of predetermined locations. For each new title to be distributed on a copy-protected record carrier, a different error pattern may be generated. In one embodiment of the error pattern, the error locations should be mixed with error-free locations or with substantial information. Furthermore, the error pattern may include a number of isolated fault locations between error-free locations, but also some consecutive faults. Preferably, the pattern of flaws is a pseudo-random pattern having approximately 50% flaws and 50% flawless locations, the pseudo-random pattern being generated by a predetermined algorithm from a seed. The error pattern must be verified in an access control procedure, which procedure is inseparably embedded in the procedure to be used for the main information. The verification should include at least one error location and preferably also at least one error-free location near a fault location. This prevents a malicious party from easily mimicking the error pattern by physically destroying some sites. A logic error is formed by a number of bit errors in the bit sequence, which number of bit errors are uncorrectable with said error correction rules. The bit errors can not be copied using a standard recorder because such a device accepts information to be recorded without error correction bits. The recorder will process this information according to the built-in, previously determined error correction and formatting rules to generate a new bit frequency, including newly generated and inherently correct error correction bits. Therefore, this new bit sequence will not contain any errors and will not be accessible to such standard recorders to change bits. The new bit sequence can be recorded on a recordable record carrier, but this copy will not contain the error pattern. It should be noted that the logic errors must be applied after the error coding step, prior to writing the physical pattern of marks in the bit sequence, so that they are uncorrectable after reading the marks with the error decoding step. Attaching errors at a higher system level prior to error coding, such as deliberately altering the EDC (Error Detection Codes) in a sector or sector header on the CD-ROM, can be easily mimicked by a malicious party because the higher level formatting process is common executed by software and therefore is accessible for manipulation. An operational but illegal copy containing the higher-level faults can be made into the attached computer system using standard recording devices and (customized) software, e.g. With a bitmap program available for making copies of audio CDs.

Since burst errors occur on the surface of a record carrier as a result of dirt or scratches, error correcting rules, such as those for correcting burst errors, are particularly useful for correcting burst errors. B. for the CD, by interleaving before saving and deinterleaving after reading. The bit errors forming such a burst error are mixed by deinterleaving rules that are part of the formatting and error correction rules with a much larger number of other bits from the bit sequence. A number of consecutive bit errors sufficient to cause uncorrectable errors must be longer than the longest correctable burst error. The error correction rules are determined by means of 3 described. In a preferred embodiment, only selected bits of the bit sequence have errors, which bits are selected to accumulate by deinterleaving, which deinterleaving is part of the formatting and error correction rules. This results in a location on the record carrier that has a high concentration of errors while adjacent locations have few or no bit errors. An example of bit errors is given by 4 described. Usually, error correction rules, and in particular deinterleaving or interleaving rules, work with symbols, e.g. For example, bytes of 8 bits are applied while the error correction process is applied to error words having a number of symbols that have accumulated through deinterleaving. The error symbols are selected so that when deinterleaving they accumulate into an uncorrectable number in one or a few error words.

A effective way To apply bit errors is the inversion of each bit from a selected one Symbol in the original one Bit sequence without error, which selected symbol with a bit error must be provided. Alternatively, the bit errors can be applied to the Symbols are applied when the symbols mentioned in the pattern of translated physical marks is, for. When using a controllable EFM encoder. For the mentioned symbols can the EFM encoder can be controlled so that some of the physical Brands change, so that they are different from the original one different brands based on the bit sequence without errors. Preferably, the resulting physical marks correspond the for The physical marks specified limitations, as this is a reliable operation ensures the reading and decoding process.

2 shows a logical mapping of the recording area of a copy-protected recording medium. The recording area is divided into addressable sectors from the top to the bottom of the address 00 to the address MAX. The first area 21 may be a lead-in area or a pre-gap area, such as: For example, the 2 second silence area on the CD. The second area is a system area 22 containing system information about the contents of the disc, such as: B. the PVD (Primary Volume Descriptor) on CD-ROM. The remainder of the disk is available for user data, such as Main information and directory files. The user data area may be subdivided into several areas, the subdivision being free and not the ones in 2 limited figure shown. In this figure, the remaining area is a third area 23 , the user files 28 covers, a fourth area 24 , which does not include user data, and a fifth area 25 that includes user data again. According to the invention, the fourth area comprises 24 a refill area (padding area) 26 , The refill area 26 has error sectors 11 indicated by the x and error-free sectors 12 which error sectors comprise the logic errors and form the error pattern. The refill area 26 may include a large number of sectors, e.g. 20 Mbytes, and may cover substantially the entire recording area that is not covered by the main information. This has the advantage that, if the presence of the error pattern needs to be verified, every time a small number or only one of the error sectors has to be selected from the large number available in the padding area. A malicious person attempting to intercept the verification will not see a recurrent test of a sector or some special sectors, but mostly different sectors will be read from a large address range to detect the presence of logic errors. This will effectively prevent the malicious party from designing simple interceptors to make it think that it is reading a sector. Another advantage can be achieved if the writable disc containing the illegal copy has a lower data capacity than the pressed disc. For example, on most CD-ROMs, much of the capacity is not in use, but can be completely replenished by the replenishment area without increasing manufacturing costs, while CD-Recordable or CD-Rewritable have a lower capacity than a maximum-filled CD. ROME. In this case, not all information (user information and replenishment area) can be transferred to the illegal copy. In one embodiment, further access control information is in the system area 22 or another area that can not be directly accessed in a standard reader, such as As the inlet, outlet or pre-gap area 21 , The further access control information could be a license code indicating the party using the copy protection system for record carriers and / or indicating the error pattern, e.g. B. must be used as a starting point in an error pattern generation algorithm.

3 shows an error correction unit which used in the CD system, called CIRC (Cross Interleaved Reed-Solomon Code). A detailed description of the CIRC error correction rules is in GB 2076569 (PH Q80009, document D2), the decoder therein being based on 7 is described. In 3 is the input (left) a frame of 32 bytes, which are stored in succession on the record carrier, indicated by the column bytes numbered 0 to 31, the 12 data bytes 0-11, four C2 error correction bytes 12-15, again twelve bytes of information 16 -27 and four C1 error correction bytes. The odd bytes are in a first delay unit 31 delayed by one cycle and the resulting error words of 32 bytes are passed through the C1 unit 32 mistake corrected. The C1 unit can correct 1 byte error and detect all 2 and 3 byte errors, while recognizing 4-32 byte errors with a very low error rate. If the C1 unit detects an uncorrectable error, it will mark all bytes as unreliable. The output of the C1 unit is through a second delay unit 33 the byte 0 is delayed by 27 × 4 = 108 frames, byte 1 by 26 × 4 = 102 frames, etc. The output of the second delay unit 33 contains a second error word, which is error-corrected by the C2 unit. The C2 unit usually corrects up to 2 errors, but can correct up to 4 bytes by erasing if the C1 unit marks all detected errors. The output of the C2 unit is passed through the descrambling unit 35 descrambled. The functions described are complementary to the inverse functions in the encoder, with all functions well known from the CD system and detailed in document D2. According to the invention, uncorrectable bit errors result in a logic error, therefore bit errors must be present in the input frames accumulating at least 2, but preferably 3 or more, errors in the error words at the input of the C1 unit. Also at least 3, but preferably at least 5 errors should be present in at least one second error word at the input of the C2 unit. For 5 errors in a second error word, this requires at least 17 consecutive error-marked output frames of C1, with errors in a group of 5 consecutively numbered information bytes. For example, errors in byte 0 in frame 0 will accumulate at the input of C2 with errors in byte 2 in frame 8 and errors in byte 4 in frame 16. For generating a cluster of logic errors within a specified data unit, such as a sector in the CD system, preferably more bit errors than the above minimum 5 errors in 17 consecutive frames should be used. Another error correction layer, as used in the error correction CD-ROM within a sector, may correct for some logic errors that are uncorrectable with the above error correction rules. Therefore, a larger number of logic errors should be included. An embodiment that achieves a secure margin without risk of spreading the errors over a large area has errors in all of the first or second twelve consecutively numbered bytes of information. These errors will be spread over 12 × 4 = 48 frames due to the second delay unit and over 1 additional frame due to the first delay unit and, because there are 24 consecutive frames with errors, over 48 + 1 + 24 = 73 frames. Since a frame comprises 24 bytes of information, this is 73 × 24 bytes = 1752 bytes, which is well within a sector of the CD-ROM format (2352 bytes), provided that the error frames are within this sector. The sector has 98 frames, so a maximum of 49 consecutive frames can have errors without affecting adjacent sectors. It should be noted that applying errors to all bytes in the frames, as would be the case if an entire area of the disk were to be corrupted, for example, by physically destroying the area, is not a solution to creating logic errors. Such errors will spread over at least 28 × 4 + 1 = 113 frames and over a minimum of 17 consecutive error frames over 130 frames. The number of bytes affected is 130x24 = 3232, which is much more than one sector.

If Errors that are uncorrectable in the C1 and / or C2 unit are, the bytes are not changed, but marked as a mistake. Bit errors in information bits lead to it Bit errors that propagate to the output of the error correction unit, while Error correction bits are used in the error correction unit and are not visible at the exit. Therefore, are in one preferred embodiment the bit errors in the information bits and not in the error correction bits.

In addition, should Bit errors are not caused by deinterlacing on adjacent sectors distribute, which should remain error-free. Therefore, in a preferred embodiment the part of the bit sequence that corresponds to error-free sectors that border on error sectors, almost no bit errors. Although some Bit errors in the adjacent sectors can be corrected a higher one Risk for uncorrectable Error, if further errors, eg. B. dirt caused by dirt, be combined with the mentioned bit errors. In this case, a error-free sector wrongly be classified as an error sector.

Although the bit errors accumulate in a few selected error words and thus directly affect only the selected locations, a large number of symbols (= bytes) will be marked as unreliable by the C1 unit (fak table all symbols in all C1 words that have 2 or more error bytes). The C2 fault unit will first compute a syndrome to detect any potential errors, which syndrome indicates if there are any errors. Further calculation will show the number of errors and possibly indicate which symbols need to be corrected. Several approaches can be used for the correction, for example, errors can be corrected directly in only 1 or 2 symbols, and for correcting 2 to 4 error symbols, the marks from the previous C1 unit can be used to indicate which symbols need to be replaced ( Correction by deletion). Usually, the C2 unit will not use C1 marks if it detects 0 or 1 errors. Therefore, the large number of marked but unchanged symbols will not be noticed by the C2 unit or classified as errors. Preferably, said sectorized format C1-marked symbols should be within the selected error sector as much as possible, as additional errors caused by dirt, etc., in combination with the C1-marked symbols, can cause uncorrectable C2 errors. For a detailed description of the error processing rules, see D2. In another embodiment using double-layer C2 / C1 error coding, errors are introduced during encoding, after the C2 encoding step, but before the C1 encoding step. Thus, no errors are detected during decoding at the CD decoder and no marking of C1 symbols occurs. At the C2 decoding step, however, the errors appear and are uncorrectable. All errors can be easily controlled to lie within a sector since interleaving and deinterleaving occurs after the C2 encoding and before the C2 decoding step. Alternatively, a combination of C2 and C1 errors can be used.

The Invention can be used in systems that are different Use error correction rules, such as B. a DVD. A corresponding Pattern of bit errors that counteract deinterleaving can can be found according to the above description. At further Applications could a refined approach to error correction a repeated application the error correction rules, by firstly outputting the first Error correction process as nested in the encoder and secondly deinterleaf and apply the error correction rules again become. Since some bugs in the first process can be corrected, one could such second error correction process correct further errors. To prevent such an approach from correcting the logic errors, the bit frequency and positioning of the bit errors are preferred such that they are uncorrectable in each error correction layer are.

4 shows a bit error pattern for the CIRC error correction rules, as in 3 described. The bit errors are designed to accumulate in the C1 error words as well as in the C2 error words, in both cases up to 5 errors. The pattern of errors can be shifted to other bytes of information (0-11, 16-27), but should cover only information bytes and no error correction bytes. In 4 errors in bytes are indicated by the letters a, b, c, d, e, while bytes are not marked without error. In order to influence 20 consecutive C1 words, 21 frames have been provided with errors, with compensation for the first delay unit 31 the odd bytes start one frame earlier and the even bytes stop one frame later. Because of the delays in the second delay unit 33 if the errors marked by the same letter accumulate in the C2 words, then 4 consecutive C2 frames will have 5 "e" errors, the next 4 C2 frames 5 "d" errors, up to the last 4 C2 Frames with "a" Errors Because there are either 0 or 5 errors accumulated in each C1 or C2 error word, no errors are compensated for, and this error scheme can easily be extended to more errors in more consecutive error words if necessary Also, it can be applied a few times within a sector to prevent a subsequent burst error correction process from correcting the logic errors 3 mentioned, the C1 correction unit has a 100% detection probability for 2 and 3 error words, while 4-32 errors could occasionally be incorrectly corrected. Therefore, a preferred embodiment that uses C1 errors has only 3 errors that accumulate in the C1 words. An effective error pattern that has the aforementioned 3 C1 errors may be 4 can be derived by using only the a, b, c errors and omitting the d and e errors. Alternatively, instead of having 4 consecutive C1 frames errors, only the first of each quad could be errored, resulting in a single C2 frame error. The error pattern beginning at byte 0, as in 4 indicates that nearly all C1-marked but unchanged bytes precede the error bytes, with the first byte being byte 27 of frame 2 preceding the logic errors by 108 frames. Only a few marked but unchanged bytes will follow after the logic errors, ie the last is byte 0 of frame 21, which is 16 frames farther. Preferably, by synchronizing the affected frames with the sectors, the marked but unaltered bytes should be positioned within the error sector, e.g. For example, the error pattern of 4 at the End of the fault sector be attached. Accordingly, most of the marked but unchanged bytes will lag behind the logic errors if the errors are applied to the highest numbered bytes (eg, 23-27).

5 shows an arrangement for retrieving information from a copy-protected record carrier 1 and to process the information. The arrangement comprises a reading unit for reading out the bit sequence from the record carrier 1 , The reading unit comprises a reading head 41 for scanning the track and generating a read signal corresponding to the physical marks on the record carrier, and a translation unit 42 for translating the read signal into the bit sequence, e.g. B. an EFM decoder for decoding in a CD system. The bit sequence is with an error correction unit 43 coupled to recover the information and correct any errors, e.g. B. with the CIRC correction unit in a CD system. The recovered information is used to control access to the information with access control means 47 coupled. The access control information is at the output 48 the access control means 47 available for further processing. When reading is the reading head 41 on the track through a servo unit 44 positioned of conventional type, while the recording medium by a motor unit 45 is turned. The reading out of information is via a controller 46 controlled, the controller being the motor unit 45 , the servo unit 44 and the error correction unit 43 controls and for receiving read commands, z. B. via an interface to the access control means 47 , is arranged. The access control means 47 may be implemented in circuits incorporated in a reading device which also includes the above reading means. This has the advantage that the information is not sent to the output 48 are supplied when the respective access control information is not on the recording medium. The access control means may also be implemented in a computer which is interfaced with a standard reader, such as a computer. B. a CD-ROM drive. In the computer, the access control means may be built into an interface card or executed by software running on a central processing unit. The software for performing access control may be provided to a user on the copy-protected record carrier. This has the advantage that no special hardware is necessary and the user has all the means necessary to access the copy-protected information contained on the record carrier.

The access control according to the invention is realized as follows. The access control means will first acquire access control information indicative of the error pattern. This access control information may be a pattern stored on the record carrier, e.g. B. the basis of 2 described license code, or one over a network, eg. Internet, or access code supplied on paper. In one embodiment, the error pattern may be generated using an output value and a previously defined algorithm, the output value being stored on the copy-protected record carrier. Second, the presence of logic errors must be verified to ensure that the disk is an original, copy-protected disk and not an illegal copy. The access control means will select one or more error locations on the record carrier or error sector (s) when the record carrier is formatted in addressable sectors, the error locations should have a logic error corresponding to the error pattern.

Third, the presence of an error is verified by reading the selected error location. Since the reading device generates an error message on the interface in the event that a sector to be read contains uncorrectable errors, the presence of the logic errors can be recognized effectively. Since a copy will not include the logic errors, the copy will be discarded and access to the information will be blocked. Preferably, some flaws will be out of a large number of flaws on the record carrier, e.g. For example, in a padding area that is to include the error sectors and error-free sectors having error patterns, are arbitrarily selected. Alternatively, the error sectors may be mixed with valid sectors comprising normal user information. In order to obtain a fast response for the access control, preferably only one error sector is selected and read out. In practice, reading a sector with uncorrectable errors could only result in a delay of a few seconds, which delay is caused by the reader attempting to read the sector a few times. Such repeated attempts are standard practice to increase the likelihood of successful recovery of information from dirt and scratches. The error pattern may be further verified by selecting at least one error-free location, but not all error-free locations, where the error-free locations should not have a logic error corresponding to the error pattern, and verifying the absence of an error by reading the selected error-free location. Since the reading of an error-free sector is very fast, z. B. in 0.2 seconds, is preferred as a larger number of error-free sectors, eg. B. 10 to 40, selected and read. Such error-free sectors are preferably selected from all available error-free sectors via a random selection process. In one embodiment, the content of the error-free sectors may be verified, for example, by including a check value in such a sector that must be derived from the sector number and the license code by a predetermined encryption algorithm. In another embodiment, error-free sectors are selected and verified before and after a selected error sector. This has the advantage that z. 21 to 81 obviously randomly selected sectors, only one of which should contain an error. This has the advantage that a malicious party will have great difficulty imitating this verification process. Since the error pattern according to the invention is designed so that all bit errors accumulate in the error sectors without affecting the adjacent sectors, it is preferable to select some error-free sectors which adjoin error sectors. This will most likely uncover illegal copies destroyed in certain areas to mimic the error pattern. The access control for a computer program can be realized as follows. The information carrier contains the computer program, while some essential data is included in the access control information. The computer program itself can be encrypted, while a short launcher takes the place of the program and controls access to the main program. The access control information may be, for example, a decoding key, a serial number or an access code or possibly a small part of the program code (a subroutine, object or module). Since it requires this essential data, the program can only function if both the information and the access control information are available. The launcher may read access control information from a hidden location on the record carrier, such as the license code, in the system area 22 is included (see 2 ) and / or other access data files. Thereafter, the presence of the error pattern must be verified as described above.

6 shows a schematic representation of the copy protection for a recording medium. The text below assumes that the invention is applied under the control of a licensor. In the first step 61 The publisher creates a new software title 71 , The publisher need not make any changes to the software in order to use the invention. The system can only be fully developed and tested. In a second step 62 The publisher encrypts the main executable file (eg, for a DOS or Windows system) to create an encrypted set of files 72 , Using a tool provided by the licensor, the publisher encrypts it using a license number as the encryption key. The licensor assigns unique license numbers for each manufactured product. For example, if the software title to be protected has a program called foo.exe, the encryption process encrypts this program, renames it foo.icd, and includes a new program supplied by the licensor, renamed foo.exe becomes. This program is then responsible for performing the security checks, verifying the license number, and opening the encrypted program (foo.icd). In a third step 63 The publisher creates from the encrypted file set 72 an image file 73 , such as For example, an ISO 9660 image. Using a CD authoring package, the publisher creates an image file 73 the full software title on a hard disk drive. In a fourth step 64 becomes the image file 73 modified to the full content 74 the copy-protected record carrier having a like in 2 has described logical mapping. A second tool provided by the licensor modifies the image file 73 by the system area 22 a license structure is added containing the license number. The image file 73 is further modified to fill the size of the image to include the padding area. The total length is preferably more than 74 minutes (333,000 sectors). The license structure contains a reference to the beginning and end sectors of the replenishment area. In the replenishment area, sectors will either be good or bad and the distribution of sectors will be determined by a pseudo-random process that can be started from the license number. At a fifth step 65 the image file is processed to a master disk 75 to create, for. By a mastering company. The image file 74 is sent to the mastering company on magnetic tape or other suitable media. Using laser beam recorder software modified according to the invention, a master disk is produced 75 produced. The Laser Beam Recorder software uses the license structure to determine which sectors in the padded area are bad and which are good. The ratio of marked to good sectors may be fixed, e.g. For example, about 50%. The errors are made according to the above based on 4 attached error patterns attached. In a sixth step 66 become copy-protected record carriers 76 , such as As CD-ROMs, by duplication of the master plate 75 produced. The error pattern is transmitted to each disk at this step.

Even though the invention by an embodiment explained Using the CD-ROM as an example, the CIRC error correction rules It will be clear that other record carriers, magnetic or optical tape, etc. may be used in the invention, if any record carrier Include information that is protected by previously defined error protection rules. For example, the high-density DVD disc also uses an error correction process. Although the invention has been described with reference to preferred embodiments is, of course be that these are not limiting examples are. So can various modifications for be apparent to those skilled in the art without being defined by the claims To leave frame of the invention. For example, applying may error patterns in error-protected Data over transmit a network be such. As the Internet, an access control according to the invention gain. About that In addition, the invention resides in each feature and each new feature or a combination of features.

preferred embodiments of the invention as follows be summarized.

The The invention relates to a copy protection method for a record carrier with according to previously certain formatting and error correction rules Information, with the steps: Creating an image file with main information, Generating access control information for controlling the access on the main information, creating a master carrier in dependence from the image file and the access control information which is establishing the following steps include: generating a bit sequence Apply the formatting and error correction rules to the image file and translate the bit sequence into a physical pattern of marks and duplicating the record carrier Use of the master carrier, according to the invention thereby characterized in that in the manufacturing step, bits in the bit sequence according to the access control information changed be used to form logic errors with the above-mentioned error correction rules can not be corrected and that form an error pattern.

Preferably at least part of the main information is dependent encrypted by the access control information. Advantageously at least some of the access control information in the image file contain and will the error pattern depending on the mentioned generated access control information generated.

The The invention further relates to a copy-protected recording medium with a bit sequence stored thereon, the information according to previously certain formatting and error correction rules, where the information main information and access control information to control access to the main information, according to the invention thereby characterized in that the bit sequence comprises bit errors, the logic errors form that does not correct with the error correction rules mentioned can be and that form an error pattern that includes at least part of the access control information represents. The measures have the advantage that the error pattern can be easily detected can, while Do not error in using a standard recorder a copy of the record carrier stored information can be contained because such recording devices have built-in error correction rules that are not tampered with can be.

Preferably is the record carrier one CD, wherein the error word correction rule is the C2 layer. advantageously, The bit errors are such that they accumulate by deinterleaving, which Unpart part of the formatting and error correction rules is. Also, the bit errors are advantageously such that they are accumulate in at least a second error word, not with a second Error word correction rule can be corrected. It is also advantageous the record carrier a CD, where the error word correction rule is the C2 layer and the second error word correction rule the C1 layer of the CD error correction rules is.

The The invention further relates to a method for detecting access control information on such a copy-protected Recording medium, characterized in that the method comprises the steps of selecting at least one flaw, but not all flaws, which error location (s) a logic error according to the previously determined error pattern should have (s), as well as verifying the presence of an error by reading the selected fault location (s).

Preferably the method comprises a step of recovering at least some, for the Error pattern indicative access control information from the main information before selecting sites. Advantageously, when the record carrier is divided into addressable sectors, the presence or absence verified a mistake in one place by the respective sector is read and an error message is generated if an uncorrectable Error while reading the sector has been detected. Also advantageously comprises the record carrier Software to the method for detecting access control information on a computer system.

The The invention further relates to a recovery arrangement for recovering information from a copy-protected record carrier, wherein the arrangement comprises reading means for reading the record carrier, wherein the reading means comprise a reading unit for extracting one the record carrier stored bit sequence and an error correcting unit for processing the bit sequence, characterized in that the arrangement Access control means for controlling the access to the information comprising which access control means for detecting the access control information by selecting at least one fault but not all faults, which error location (s) should have a logic error according to the error pattern (s), and by verifying the presence of an error by reading the selected fault location formed by means of the reading means are. This is advantageous in that it selects some flaws from one available larger number leads to a fast response of the access control means. Read a sector with errors can be displayed on a standard recorder, such as As a CD-ROM, due to automatic repeated attempts take up to 30 seconds. Also the selection of different ones Ask for each access control session increases the difficulties for a malicious one Party to mimic the access control process.

Preferably, if the record carrier is divided into addressable sectors, the reading means comprise a control unit for controlling the reading of a sector and the Generate an error message if an uncorrectable error has been recognized.

The The invention is also based on the following finding. physical damage selected Parts of a record carrier leads to faulty physical marks. When reading such damaged parts For example, a read head may lose track or the translation of the read signal into a bit sequence can be disturbed or lose synchronization, resulting in an uncontrollable number Leads to errors. About that In addition, physical damage easily detected from physical parameters and imitated by physical means by a malicious party become. Also increased a physical damage of sectors the manufacturing costs. The invention is based on a logical pattern of errors that does not increase the manufacturing costs and a precise control of the resulting errors allowed. In addition had the inventors realize that physical defects are not for Generate errors in a limited part of the recovered information can be used because they are similar to bundle errors, an error type resulting from deinterleaving steps commonly used in an error correction and de-formatting process for recovering the information applied to the bit sequence is widely used is. Therefore, one embodiment the copy-protected record carrier characterized in that, during the bit sequence comprises information bits and error correction bits, the information bits comprise the bit errors and / or the bit errors lie in such a way that they accumulate in a mistake word, that when playing is uncorrectable by an error word correction rule. This is advantageous in that the bit errors are concentrated in error words are those that clearly result in logic errors while there are no error bits to other parts of the recovered Spread information.

A another embodiment the copy-protected Recording medium, the record carrier is divided into addressable sectors, is characterized that the record carrier a refill area (Padding area) comprising fault sectors and error-free sectors, where the error sectors include the logic errors and the error pattern form. Using sectors as primitives for the error pattern has the advantage that standard readers read the information read and process on a sector-by-sector basis, generating an error message if there is an uncorrectable error detected somewhere in a sector has been.

A another embodiment the copy-protected record carrier is characterized in that the part of the bit sequence, the error-free Almost equal none of the sectors bordering on error sectors Includes bit error. In the case of some dirt or scratches will be the affected sectors are random or small bundle errors exhibit. If such errors in the presence of intended Bit errors would have to be corrected, would be one increased Risk occur that a faultless sector as a fault sector would be classified. Almost no intending to have bit errors has the advantage that the probability of misclassifying error-free sectors, is low.

Another embodiment of the copy-protected recording medium is characterized in that, while the recording medium has a predetermined information storage capacity of which the main information covers a part, the padding area nearly covers the remaining part of the information storage capacity. This has the following advantage. All logic errors that make up the error pattern can only be detected when the entire padding area is read. On an average record carrier, a relatively large percentage of the information storage capacity available for the error pattern may be unexploited without increasing manufacturing costs. For example, with a reading time of 20 seconds for a sector that has errors due to repeated attempts, it will take more than 1000 hours to read the entire padding area on a 60% unused capacity CD-ROM.

A embodiment of the method for detecting access control information characterized in that the method further comprises the steps selecting at least one error-free location, but not of all error-free jobs includes which error-free job (s) no logic error according to the error pattern and verifying the absence of an error by reading the selected error-free location (s). This is insofar advantageous as an illegal copy that also errors on error-free Has points, is detected.

A another embodiment of the method for detecting access control information characterized in that at least one error-free location selected which is adjacent to an error location. This is advantageous in that as an illegal copy, physical errors or bundle-type errors which, due to deinterleaving rules, has more Spread out, is detected.

Inscription of the drawing

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Claims (29)

Copy protection method for a record carrier with information stored thereon according to previously defined formatting and error correction rules, wherein the record carrier is subdivided into addressable sectors, the record carrier is a padding area ( 26 ), the error sectors ( 11 ) and error-free sectors ( 12 ), the error sectors contain logic errors and the error-free sectors do not contain uncorrectable errors, comprising the steps of: (a) creating an image file with main information, ( 63 ) (b) generating access control information for controlling access to the main information, ( 64 ) (c) producing a record carrier in dependence on the image file and the access control information ( 65 ), comprising the steps of: generating a bit sequence by applying the formatting and error correction rules to the image file, changing bits in the bit sequence according to the access control information to form logic errors that can not be corrected with the error correction rules and those previously defined Forming error patterns, - translating the modified bit sequence into a physical pattern of marks on the record carrier where the logic errors are stored in the padding area, (d) duplicating the record carrier using a master carrier, 66 (e) selecting at least part of the physical pattern of marks on the record carrier which selected part should have a logic error according to the predetermined error pattern, (f) reading the selected part of the physical pattern of marks on the record carrier, and (g) Controlling access to the main information on the record carrier in response to the presence of an error in the selected part of the physical pattern of marks on the record carrier. Method according to claim 1, in which at least a part the main information in dependence is encrypted by the access control information. The method of claim 1, wherein at least some the access control information is contained in the image file and the previously defined error pattern depending on the contained Access control information is generated. Copy protected record carrier ( 1 ), wherein the carrier is subdivided into addressable sectors, comprising: a substrate and a padding region ( 26 ), the error sectors ( 11 ) and error-free sectors ( 12 ), wherein the error sectors include logic errors and the error-free sectors do not contain uncorrectable errors, a correctable bit sequence stored thereon that represents information according to previously defined formatting and error correction rules, the information comprising main information ( 23 . 24 . 25 ) and access control information ( 21 . 22 . 26 ) for controlling access to the main information, the bit sequence comprising bit errors, the logic errors ( 2 ) that can not be corrected with the error correction rules and that form a previously defined error pattern that represents at least part of the access control information, the previously defined error pattern being defined by errors and the logic errors stored in the padding area. A support according to claim 4, wherein the support comprises the following areas: a first area, e.g. A lead-in area or a pre-gap area, a second area with system information about the contents of the plate, a third area containing the replenishment area. 26 ), a fourth area comprising user data. carrier according to claim 4 or 5, wherein the part of the bit sequence is the error-free one Corresponding sectors bordering on error sectors are not uncorrectable Includes bit error. A carrier as claimed in claim 4 or 5, wherein the record carrier has a predetermined information storage capacity of which the main information covers a part and the padding area (Fig. 26 ) covers the remaining part of the information storage capacity. carrier according to claim 4 or 5, wherein the bit sequence information bits and error correction bits and the information bits contain the bit errors leading to logic errors to lead, and the error correction bits do not have bit errors that result in logic errors. carrier according to claim 4 or 5, wherein the bit errors indicative of the logic errors Worries are so that they accumulate more in at least one error word than in another error word, and that one error word during the Playback can not be corrected with an error word correction rule. carrier according to claim 9, wherein the record carrier is a CD and the error word correction rule contained in the C2 layer. carrier according to claim 9, wherein the bit errors that cause the logic errors, so lie that they accumulate by deinterleaving, which deinterleaving Part of the formatting and error correction rules is. carrier according to claim 9, wherein the bit errors that cause the logic errors, so lie that they accumulate more in at least a second error word than in another second error word, and that a second error word while playback is not corrected with a second error word correction rule can be. carrier according to claim 12, wherein the record carrier is a CD, wherein the Error word correction rule the C2 layer and the second error word correction rule is the C1 layer of the CD error correction rules. Method for detecting access control information on a copy-protected record carrier ( 1 ) according to one of claims 4 to 13, comprising the steps of: - selecting at least one fault location ( 11 ), but not all flaws, which flaw (s) a logic error ( 2 ) according to the previously defined error pattern, and verifying the presence of the logic error by reading the selected error location and detecting the logic error during the error correction. The method of claim 14, wherein the method further comprises the steps of: selecting at least one error-free location ( 12 ), but not all error-free places, which error-free place no logic error ( 2 ) according to the previously defined error pattern, and verifying the absence of a logic error by reading the selected error free location and detecting the uncorrectable error. The method of claim 14, wherein at least one error-free location is selected, which borders on a fault location. The method of claim 14, further comprising Step of recovering at least some, for the error pattern of significant access control information from the Main information before selecting bodies. The method of claim 14, wherein the record carrier is addressable Sectors is divided and the presence or absence of a Logic error is verified at one point by during the Error correction read the respective sector and the logic error is recognized. carrier according to claim 4, wherein the record carrier comprises software to perform the Method according to one of the claims 14 to 18 on a computer system. Computer program product that includes software that to run the method according to any one of claims 14 to 18 is formed, when running on a computer system. A retrieval arrangement for retrieving information from the copy-protected record carrier of any one of claims 4 to 13, the arrangement comprising reading means for reading the copy-protected record carrier, the reading means comprising a reading unit (16). 41 . 42 ) for extracting a bit sequence stored on the record carrier and an error correcting unit ( 43 ) for processing the bit sequence, the arrangement including access control means ( 47 ) for controlling the access to the information according to detected access control information by selecting at least one fault location ( 11 ), but not all flaws, which at least one flaw a logic error ( 2 ) according to the previously determined error pattern, and by verifying the presence of the logic error by reading the selected error location by means of the reading means and detecting the logic error during the error correction. Recovery arrangement according to claim 21, wherein the record carrier is in addressable sectors is divided and the reading means a control unit for controlling reading a sector and generating an error message, if an uncorrectable error has been detected, included. Recorder for producing the copy-protected record carrier ( 1 ) according to one of claims 4 to 13, comprising means for providing an image file with main information ( 23 . 24 . 25 ); Means for generating access control information for controlling access to the main information; Means for producing a record carrier in dependence on the image file and the access control information, comprising the steps of: generating a correctable bit sequence by applying the formatting and error correction rules to the image file, modifying the correctable bit sequence according to the access control information ( 21 . 22 . 26 ), logic errors ( 2 ) which can not be corrected with the error correction rules and which form a previously defined error pattern, and translating the modified bit sequence into a physical pattern of marks on the record carrier where the logic errors in the padding area ( 26 ) get saved. Player for detecting access control information ( 21 . 22 . 26 ) on a record carrier ( 1 ) according to one of claims 4 to 13, for accessing other information on the record carrier, comprising: means for selecting at least one error location, but not all error locations on a record carrier, which error location is a logic error ( 2 ) according to a previously defined error pattern, and means for verifying the presence of a logic error by reading the selected error location and detecting an uncorrectable error during the error correction. Record carrier subdivided into addressable sectors with a substrate, a padding area ( 26 ), a bit sequence that represents information in accordance with previously defined formatting and error correction rules, the information containing main information ( 23 . 24 . 25 ) and access control information ( 21 . 22 . 26 ) for controlling access to the main information, a license structure comprising instructions for performing the following steps: changing the bit sequence according to the access control information to avoid logic errors ( 2 ) which can not be corrected with the error correction rules and which form a previously defined error pattern, translating the modified bit sequence into a physical pattern of marks on the record carrier where the logic errors are stored in the padding area, the padding area being error sectors and error-free sectors where the error sectors contain the logic errors and the error-free sectors do not contain uncorrectable errors. record carrier according to claim 25, wherein the previously defined error pattern Defects and error-free places is defined. A record carrier according to claim 25 or 26, wherein the license structure further includes a reference to the beginning and ending sectors of the padding area ( 26 ). record carrier according to claim 25, 26 or 27, wherein the license structure continues includes a license number. record carrier according to claim 28, wherein the previously defined error pattern of the license number goes out.